allwpilib/upstream_utils/json_patches/0019-Add-to_json-from_json-and-json_serializer-struct.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Peter Johnson <johnson.peter@gmail.com>
Date: Fri, 3 Apr 2026 23:01:45 -0700
Subject: [PATCH 19/25] Add to_json, from_json, and json_serializer struct

---
 json.h | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)

diff --git a/json.h b/json.h
index 62af49cb18b713304ad95e89c52f5cc5bbc4b626..e52435a79ee7537928ba59fb146f635fc8511bfc 100644
--- a/json.h
+++ b/json.h
@@ -26,6 +26,35 @@
 
 namespace wpi::util {
 
+class json;
+
+template <typename T>
+struct json_serializer;
+
+namespace detail {
+template <typename T>
+concept HasToJson = requires(json& j, const T& val) {
+    { to_json(j, val) };
+};
+
+template <typename T>
+concept HasFromJson = requires(const json& j, T& val) {
+    { from_json(j, val) };
+};
+
+template <typename T>
+concept HasJsonSerializer = requires (json& j, const json& cj, const T& val) {
+    typename json_serializer<typename std::remove_cvref_t<T>>;
+    { json_serializer<typename std::remove_cvref_t<T>>::to(j, val) };
+};
+
+template <typename T>
+concept HasJsonDeserializer = requires (json& j, const json& cj, const T& val) {
+    typename json_serializer<typename std::remove_cvref_t<T>>;
+    { json_serializer<typename std::remove_cvref_t<T>>::from(cj) } -> std::convertible_to<typename std::remove_cvref_t<T>>;
+};
+}  // namespace detail
+
 class json
 {
     friend bool operator==(const json& lhs, const json& rhs);
@@ -152,6 +181,18 @@ class json
     {
     }
 
+    template <detail::HasToJson T>
+    json(const T& value) : type_(Type::Null)
+    {
+        to_json(*this, value);
+    }
+
+    template <detail::HasJsonSerializer T>
+    json(const T& value) : type_(Type::Null)
+    {
+        json_serializer<T>::to(*this, value);
+    }
+
     constexpr Type type() const
     {
         return type_;
@@ -214,6 +255,18 @@ class json
     object_t& get_object();
     const object_t& get_object() const;
 
+    template <detail::HasFromJson T>
+    T get() const {
+        T value;
+        from_json(*this, value);
+        return value;
+    }
+
+    template <detail::HasJsonDeserializer T>
+    T get() const {
+        return json_serializer<T>::from(*this);
+    }
+
     bool contains(std::string_view) const;
 
     json* lookup(std::string_view);
@@ -228,6 +281,18 @@ class json
     json& operator=(const json&);
     json& operator=(json&&);
 
+    template <detail::HasToJson T>
+    json& operator=(const T& value) {
+        to_json(*this, value);
+        return *this;
+    }
+
+    template <detail::HasJsonSerializer T>
+    json& operator=(const T& value) {
+        json_serializer<T>::to(*this, value);
+        return *this;
+    }
+
     json& operator[](size_t);
     json& operator[](std::string_view);